Shock inducing well tool



Oct. 5, 1965 R. 1 EssARY SHOCK INDUCING WELL TOOL 4 Sheets-Sheet 1 Filed June '7, 1962 III FIG.

FIG.

INVENTOR:

R. I ESSARY BY: kg'

HIS AGENT Oct. 5, 1965 R. L. EssARY SHOCK INDUCING WELL TOOL 4 Sheets-Sheet 2 Filed June 7, 1962 HIS AGENT Oct. 5, 1965 R. EssARY SHOCK INDUCING WELL TOOL 4 Sheets-Sheet 3 Filed June 7, 1962 mvENToR:

ROY l.. EssARY Q BY 1-H314.

ive

FIG.

HIS AGENT Oct. 5, 1965 R. L.. EssARY SHOCK INDUCING WELL TOOL 4 Sheets-Sheet 4 Filed June 7, 1962 l "in,

FIG.

FIG.

INVENTOR:

ROY L. ESSARY BY. HM:

HIS AGENT United States Patent O 3,209,834 SHOCK INDUCING WELL TOOL Roy L. Essary, Roswell, N. Mex., assignor to Shell ii Company, New York, N.Y., a corporation of Delaware Filed June 7, 1962, Ser. No. 202,935 13 Claims. (Cl. 166-177) The present invention relates to the stimulation of oil, gas or Water wells and pertains more particularly to an apparatus for stimulating fluid flow in the vicinity of a well bore by the application of shock waves and flushing action to the interval of formation transversed by the well bore that is open to production or injection. The instant application is a continuation-in-part `of my copending application Serial No. 75,231, filed December 12, 1960, now abondoned.

Many different well stimulation methods have been devised for increasing the injectivity or productivity of oil and gas wells. In general, these treating techniques fall into three broad classifications: explosives, chemicals and hydraulic pressure. The principal explosive techniques are nitro shooting and both bullet and jet perforating. Chemical treatment techniques include use of acids, surfactants, organic solvents, etc. For a number of years now hydraulic pressure has been used extensively to open and extend fractures in formations traversed by a well.

A recent development is the creation of an implosion with the shock wave and flushing action resulting from the implosion being applied to a selected interval of the well. An implosion is the movement of a high pressure surrounding medium into a low pressure zone 'or void. When an implosion is generated, there is an initial decrease in pressure within a well bore followed by a surge of increa-sed pressure. The area of maximum effect is immediately adjacent the point of the implosion. This maximum force radiates outwardly in a horizontal radial plane into the formation.

It is a primary object of the present invention to provide a well treating tool adapted to be lowered to a predetermined level within a well for subjecting the surrounding formation at that level to one or more pressure surges or shocks.

No efficient and inexpensive method or tool exists at present for removing insoluble precipitates such as calcium and barium sulfates from perforations and formation flow channels near a well bore. It is therefore a further object of the present invention to provide a downhole shock-inducing tool for breaking up precipitates of this type to the extent that they may be removed from a well by a bailer or other conventional apparatuses.

Economics often preclude the expensive stimulation treatments of low reserve, low capacity wells. Often the low capacities result from a build-up of sediments or precipitates at or near the formation face of the producing interval. It is therefore another object of the present invention to provide a downhole shock-inducing tool for inexpensively creating multiple small fractures in the formation traversed by the well with subsequent increase in fluid flow into the well.

Still another object of the present invention is to provide a downhole shock-inducing tool for inexpensively shocking and/or flushing a preselected formation tranversed by a well to remove or reduce fluid ow restrictions in the formation in order to increase injection rates into the formation.

Formation breakdown pressures are occasionally so high as to preclude hydraulic fracture treatment of a well without first initiating fractures by some other means. It is a further object of the present invention to provide an ACC inexpensive apparatus for initiating fractures in a preselected formation of the well.

In initiating fractures in a multi-Zone Well, considerable time is expended in setting up the fracturing equipment at a point opposite the several zones to be treated. It is therefore another object of the present invention to provide a downhole shock-inducing tool which may be quickly moved from one zone within a well to another for initiating fractures in the zones.

These and other objects of this invention will be understood from the following description taken with reference to the drawing, wherein:

FIGURES 1 to 8 are diagrammatic views taken in partial longitudinal cross-section of different arrangements of the downhole shock-inducing tool of the present invention when positioned within the bore of a well; and,

FIGURE 9 is a cross-sectional view taken on line 9-9 of the FIGURE 6 arrangement of the invention.

Referring to FIGURE 1 of the drawing, a well is shown as being provided with a casing 11 having a series of perforations 12 through the wall thereof opposite the producing formation 13. Positioned within the well casing 11 is the downhole shock-inducing tool of the present invention comprising a housing member 14, preferably tubular in shape and having formed therein a chamber 15. Fixedly secured to the housing member 14, for example, at the lower end thereof, is a suitable type of slip body 16 having a plurality of outwardly-extensible serrated-faced slips 17 carried thereby and adapted to anchor themselves against the inner wall of the well casing 11 to locate and prevent downward movement of the shockinducing tool. The slip body 16 is also provided with a pair of centering springs 18 which furnish enough friction against the walls of the Well casing 11 whereby the slips 17 can be readily actuated in one type of a conventional slip mechanism. When the tool and slip mechanism are run into the well, the slips 17 are in an inwardly-retracted and inoperative position so that they do not contact the inner Wall of the casing 11. On reaching the desired depth at which the tool is to be located, an upward force is applied from the surface to pick up the tool and move it up the well a slight distance. This pick-up action is sufiicient to release the slips 17 causing them to spring outwardly and engage the inner wall of the Well casing and become anchored against the casing well when the tool is again lowered. Since slips whicm operate in this manner are well kown to the art and since their particular construction and operation do not form part of the present invention, they will not be further described here.

The housing member 14 of the present tool is provided with one or more fluid ports 21 through the wall thereof which are normally closed by a suitable valve which is preferably a tubular sleeve valve element 22 slidably mounted for limited movement within the housing member 14. The sleeve valve 22 is provided with one or more fluid ports 23 spaced in a manner to register with the fluid ports 21 in the housing member 14 when the valve is in its open position. A compression pring 24 is positioned in the lower end of the chamber .1S Within the housing member 14 for exerting a pressure against the bottom of the sleeve valve 22 normally tending to open the valve. If desired, the lower end of the sleeve valve 22 may be provided with a port 25 which permits the escape of huid therefrom as the sleeve valve 22 is pushed to its lowermost position, as illustrated in FIGURE l.

Arranged within the housing member and carried there by are suitable valve-positioning or restraining devices, preferably in the form of one or more latehing dogs 26 which are pivotally secured to the housing member and arranged to engage the sleeve valve 22 so as to normally hold the valve 22 in its lowermost position, as illustrated in FIGURE l. The latching dogs 26 are released from the position shown in FIGURE 1 by being engaged by a pair of mating spurs 27 atlixed to a piston rod 28 which is arranged for vertical movement up and down within the housing member 14 and out the top thereof. A piston 30 is carried at the lower end of the piston rod 23, the piston 30 forming by means of ports 31, passageway 32 and chamber 33, a valve cage for a check valve 34 of a conventional type which forms a traveling valve at the lower end of the piston rod 28. A weight bar 35 is preferably secured to the top of the piston rod 2S to give the piston rod suicient weight to force itself and the sleeve valve 22 downwardly to compress the spring 24. The weight bar 35 and piston rod 28 and piston 39 are preferably raised and lowered from the surface by means of cable, wire line, or tubing string secured to the top of the weight bar 35. The diameter of the housing member 14 and the slips carried thereby is sufficiently small to pass down through the well casing 11. The length of the chamber 15 within the housing member 14 may be anywhere from 2 feet or more in length depending upon the size of the chamber it is desired to employ.

In the operation of the downhole shock-inducing tool illustrated in FIGURE l of the drawing, after the slips 17 have been set against the inner wall of the well casing 11 in a manner described hereinabove, any tension on the cable 36 is slacked oftr allowing the cable 36 to move downwardly within the well with the weight bar 35 forcing the piston and piston rod 28 down through the tubular sleeve valve 22 until it touches the bottom thereof. The weight of the piston 30, the piston rod 23 and/or the weight bar is suicient to force the sleeve valve 22 downwardly so as to compress the spring 24 below the valve and allow the latching dogs 26 above the sleeve valve 22 to swing outwardly and engage the top of the sleeve valve 22, thus holding it down against the compressed spring 24 with the Huid ports 23 of the sleeve valve 22 out of register with the Huid ports 21 in the wall of the housing member 14. At the time the piston 30 moves downwardly within the chamber 15, any well uid below the piston 30 passes up the passageway 32 in the piston 30, lifting the ball valve 34 and then flowing through the chamber 33 and out the fluid ports 31 in the top of the piston.

It is to be understood that during the operation of the above-described tool the well casing 11 contains a substantial amount of iluid, preferably uid from the producing formation, and if desired the well casing may be entirely full of liquid. To create a shock down in the well casing 11 at a point where the tool is located, tension is applied to the lifting cable 36 and the weight bar 35, piston rod 28 and piston 30 are pulled upwardly. During this action the ball valve 34 drops on its seat in the position illustrated in FIGURE 1 and all fluid within the chamber 15 above the piston 30 is lifted upwardly and discharged out ports 37 in the top yof the housing member 14. Since the sleeve valve 22 is closed at the time the piston 30 is moving upwardly, a void is created within the chamber 15 below the piston 30 as chamber-evacuating means in the form of the piston evacuates the chamber thereby creating a condition of reduced pressure within the chamber below the piston 30. At the top of the piston stroke the spurs 27, or other suitable latch releasing devices carried by the piston 30 or piston rod 28, engage and release the latching dogs 26, pulling them inwardly. When the latching dogs are released, the traveling sleeve valve 22 is driven upwardly by the driving spring 24 causing the several relatively large ports 23 in the sleeve valve to register with the port 21 in the wall of the housing member 14. Bringing the void chamber below the piston 30, as illustrated in FIGURE 2, into sudden communication with the fluid outside the housing member 14 within the well casing 11 creates a sudden release of pressure in the form of an implosion with a subsequent shock wave and fluid hammer created by the hydrostatic head of fluid above the tool in the Well. A series of subsequent shocks can be applied in the same manner by again coclring the tool in a manner described hereinabove with regard to FIGURE 1 and firing the tool in a manner described with regard to FIGURE 2 of the drawing.

Once the slips 17 have been set against the wall of the casing 11, the tool may be cocked and tired repeatedly with the slips preventing downward travel of the tool within the casing. Upward travel of the tool could only occur after complete extension of the piston rod 28. The tool is preferable designed so that the weight of the tool is suihcient to prevent premature upward travel of the complete tool. It is realized that other types of valves may he employed in the tool. For example, the sliding valve 22 need not be tubular. In a like manner other devices may be employed for locating the housing member 14 and limiting its movement within the well. For example, instead of employing the slip body 16 and slips 17 of FIGURE 1, a tail pipe 40 (FIGURE 3) may be employed which extends from the tool down to the bottom of the well or to a plug therein.

Additionally, as illustrated in FIGURE 3 the working portions of the tool may be reversed with the piston 30 being held stationary in the well while the housing member 14 is attached to a cable or pipe string 41 which extends to the surface, whereby the housing member 14 may be moved up and down in a manner previously described hereinabove with regard to FIGURES l and 2. In the arrangement of the apparatus illustrated in FIG- URE 3, the latching dogs 26 are mounted at the bottom of the tool while the compression spring 24 is mounted at the top of the tool. Also, in the arrangement of FIG- URE 3 the check valve carried by the piston 30 is of the spring-loaded apper type 42 instead of the ball type.

While the slip body 16 and the slips 17 are illustrated in FIGURE 1 as being carried at the bottom of the housing member 14, it is to be readily understood that they could be also mounted at the top of the housing member 14, as illustrated in FIGURE 4 of the drawing. They would be employed, when set in their operative position, to hold the tool against further downward movement in the well casing, with the weight of the tool being suicient to prevent its upward movement during operation.

Rather than employing the latching dogs 26 of FIG- URE 1, the arrangement in FIGURE 4 employs a compression spring 43 positioned above the sleeve valve 22 for maintaining the sleeve valve 22 in a normally closed position, as illustrated. In the operation of the tool illustrated in FIGURE 4, a void is created in the chamber 15 below the piston 30 during upward travel of the piston 30. When the piston 30 reaches the top of the sleeve valve 22 it contacts shoulder 44 and pulls the sleeve valve 22 upwardly against the force of the spring 43 so that the fluid ports 23 in the valve are brought in register with the ports 21 in the housing member 14, thus putting the void chamber below the piston 30 in communication with the fluid in the well casing outside the housing member 14. At this point there is a substantial energy release through shock wave and hammer action which is applied to the porous producing formation 13 through the perforations 12 in the Well casing 11. An instantaneous heavy flushing action is thereby created. The downhole shock-inducing tool of the present invention depends upon the formation pressure and the hydrostatic head of the luid column in the well casing for its basic energy component. Energy released by the tool is controlled by varying the fluid level within the Well casing, varying the type of fluid, which is normally oil or water, and/or varying the size of the tool utilized and hence the size of the void chamber created.

The tool illustrated in FIGURE 5 is similar to that shown in FIGURES l and 2 except that the slips 17 have been positioned at the top of the tool.

FIGURES 6 to 9 illustrate embodiments of the invention incorporating a modied form of shock-inducing structure. The details of these respective gures differ from each other mainly in the activating and locating means used in combination therewith. Corresponding components of the internal structure shown in each of these gures will be designated by like numerals.

Referring now to FIGURE 6, there is shown a modified embodiment of the shock-inducing tool of the present invention disposed in a well casing 11 corresponding to that shown in FIGURES l to 5. The casing 11 is provided with a series of perforations 12 through the wall thereof opposite a producing formation 13, or a formation to be treated, into which the casing extends.

In the FIGURE 6 embodiment of the invention, the numeral 45 designates the housing member of the downhole shock-inducing tool. The housing member 45 is cylindrical in shape and has a chamber 46 extending axially therein with ports 47 extending through the wall thereof into the intermediate portions of said chamber. The ports 47 are defined by annularly spaced vanes 48 lixedly secured to upper and lower sections 49 and 50, respectively, of said housing member to maintain said sections in spaced relationship with respect to each other. The housing member further includes a passage 51 extending through the lower section thereof into communication with the lower portion 46a of the chamber 46. A check valve 52 is interposed between the passage 51 and the lower portion 46a of the chamber to permit fluid ow from said portion of the chamber while preventing fluid iiow into said portion of the chamber. The upper section 49 of the housing member is provided with large and small passages 53 and 54, respectively, extending through the walls thereof into communication with the upper portion of the chamber 46.

A piston 57 is slidably disposed within the chamber 46 and provides means whereby the lower portion 46a of said chamber may be evacuated. Upper and lower sealing rings 58 and 59, respectively, are disposed around the periphery of the piston 57 to assure sealed engagement between the piston and the walls of the chamber 46. By providing a sealed and slidable engagement between the piston 57 and the walls of the housing surounding the lower portion 46a of the chamber, the piston may be utilized to evacuate the lower portion 46a on downward movement and to create a condition of reduced pressure within said lower portion on upward movement. Hence, the piston forms chamber-evacuating means. The sealing rings 58 and 59 also function as valve means to isolate the lower portion 46a of the chamber from the ports 47 disposed around the housing member. These valve means function to open the port means 47 to the lower portion of the chamber upon upward movement of the lower edge of the ring 59 beyond the lower edge of the port 47. A more detailed description of the operation of the piston and valve means will be developed subsequently hereinbelow.

A cylindrical receiving member 60 is tixedly secured to the upper surface of the piston 57 to provide for the connection of a piston rod 61 to the piston. The interior of the receiving member 60 includes a necked-down section 62 and an enlarged section 63 having large and small openings 64 and 65, respectively, extending through the wall thereof. The piston rod 61 is adapted to be slidably engaged by the receiver 60 through a shank portion 68 extending slidably through the necked-down portion 62 of the receiver and an enlarged head portion 69 secured to said shank portion and received within the enlarged section 63 of the receiver. The head portion 69 is dimensioned so as to slide as a piston within the enlarged section 63. Thus, sliding movement of the head portion 69 within the enlarged section 63 forces fluid through the openings 64 and 65. The flow of fluid through the openings 64 and 65 is restricted by the relatively small areas of these openings and thus, relative movement between the piston rod and piston is cushioned. The connection between the piston rod 61 and the piston 57 further includes a tension coil spring interposed between the piston and the piston rod. The tension spring 70 is secured to the piston and piston rod by retaining members 71 and 72 fixed to the piston and piston rod, respectively. The retaining member 72 is carried by cushion piston 73 fixed intermediate the ends of the piston rod 61.

The housing member 45 of the FIGUREl 6 embodiment of the invention is secured within the well casing by slips 74 and 75 having serrated faces extensible into engagement with said casing. The slips 74 and 75 extend from body members 77 and 78 secured to the upper and lower ends, respectively, of the housing 45 and are operated in a manner corresponding to the operation of the slips 17 heretofore described. The housing member 45 is maintained in axial alignment with the well casing 11 through means of centering springs 79 secured to the housing member and slidably engaging the well casing, and preferably by means of the vanes 48 secured to the intermediate portion of the housing member. The vanes 48, as clearly illustrated in FIGURE 9, extend radially from the housing into sliding engagement: with the well casing Il.

In operation of the tool, as will be described in detail subsequently, reciprocating movement is imparted to the piston 57. This movement is imparted to the FIGURE 6 embodiment as through a cable 80 secured to the upper end of the piston rod 61 and extending to the top of the well. In order to move the piston upwardly, tension is applied to the cable 80 from a pulling means disposed at the top of the well. The weight of the housing member 45 and the components of the tool ixedly secured thereto may be sufficient to prevent the housing from being pulled up with the piston 57. However, preferably the housing is secured against upward movement by the upper slip members 75. Downward movement is imparted to the piston 57 by slackening the tension on the cable 80. The i slip members 74 extending between the housing member 45 and the well casing 11 assure that the housing member will not move downwardly with the piston. Preferably, the piston rod 61 is provided with a weight bar 81 of sufficient weight to impart downward movement to the piston rod and piston.

FIGURE 7 illustrates a modified embodiment of the shock-inducing tool described in detail with reference to FIGURES 6 and 9. Like numerals in FIGURES 6 and 7 designate corresponding parts. Upon observation, it can be seen that the internal chamber, piston and piston rod structure of FIGURE 7 correspond to those of FIGURE 6. The FIGURE 7 embodiment differs from that of FIGURE 6 primarily in the locating means used in cornbination therewith, and the activating means used to impart reciprocating movement to the piston rod. The piston rod 61 of the FIGURE 7 embodiment is activated by a hydraulic motor 82 operatively connected to the upper end of the rod. The hydraulic motor 82 is of a relatively conventional type, generally employing a lluid driven piston member adapted to reciprocate in opposite directions. The motor 82 is fixed to the upper end of the housing member 45 and has centering springs 84 extending radially therefrom into sliding engagement with the well casing 11. Through means of the centering springs 84 and the radially extending vanes 48 of the housing member, the shock-inducing tool and the hydraulic motor xed thereto are maintained in axially aligned relationship with the well casing 11.

The tool and hydraulic motor of the FIGURE 7 embodiment are maintained at the desired level within the well casing by a conduit 85 secured to the motor 82 and extending to the top of the well. In addition to functioning as a means of suspension for the tool within the Well casing, the conduit 85 is operatively associated with the hydraulic motor 82 to provide hydraulic actuating fluid therefor. In operation, the conduit 85 communicates with a source of fluid at the top of the well and acts as a means to convey this fluid to the hydraulic motor 82.

It is noted that the hydraulic activating motor 82 of the FIGURE 6 embodiment obviates the necessity of locating means in the form of locating or anchoring slips, such as the slips 74 and 75 shown in FIGURE 6, since the housing member of the shock-inducing tool is not subjected to external pushing or pulling forces. Thus, in FIGURE 7, the conduit 85 serves as the sole locating means to locate the shock-inducing tool at the desired level. The conduit 85 may be fabricated of rigid or flexible material, depending upon the type of handling means desired to be used in combination therewith.

FIGURE 8 illustrates another embodiment of the shockinducing tool of the present invention, incorporating internal characteristics corresponding to those described with reference to FIGURES 6 and 7. As in the previously described figures, like numerals in FIGURE 8 designate components corresponding to those of the aforedescribed embodiments. The FIGURE 8 embodiment is similar to that of FIGURE 7 in that it obviates the necessity of locating or anchoring slips to maintain the tool at the desired level. The FIGURE 8 embodiment differs from that of FIGURE 7 primarily in the details of the activating means used to impart the reciprocating movement to the piston rod. The activating means in FIGURE 8 comprises an electric motor 87 fixed to a housing 88 secured to the upper end of the housing member 45. The electric motor imparts movement to the piston rod 89 through means of a screw 90 threadingly engaging the piston rod at 91. In order to impart reciprocating movement to the piston 57, the motor 87 may be either reversible or, preferably, incorporate a reversing gear arrangement. With either the reversible motor or gear arrangement, an automatic reversing mechanism may be utilized to reverse the direction of the piston at the end of a stroke thereof. It is noted that the piston rod 89 of the FIGURE 8 embodiment differs from the rod 61 of the FIGURES 6 and 7 embodiments only in that it is adapted to threadingly receive the screw 91D.

The tool of the FIGURE 8 embodiment is located at the desired level within the well casing 11 by a cable or conduit 92 secured to the upper end of the housing 88. In addition to acting as a locating means, the conduit 92 houses electrical leads 93 adapted to convey electrical energy to the motor 87. The conduit 92 and the leads 93 passing therethrough extend to the top of the well and to a source of electrical energy, such as a generator. The housing member of the FIGURE 8 embodiment is maintained in axially aligned relationship with the well casing 11 by centering springs 94 fixed to the housing 88 and slidably engaging the well casing, and by the vanes 48 of the housing member 45.

The operating characteristics of the embodiments shown in FIGURES 6 to 8 differ from each other only in the locating and activating means used in combination therewith. Therefore, the description of operation to be developed subsequently is equally applicable to each of the FIGURES 6 to 8 embodiments. In operation, the shockinducing tool is first located at the desired level within the well casing 11. The activating means is then utilized to force the piston rod down and thus force the piston 57 to the bottom of the chamber 46. As the piston 57 moves downwardly in the chamber 46, fluid within the lower portion 46a of the chamber is ushed out through the spring-loaded check valve 52. The piston rod is then moved upwardly, thus extending the accelerating spring 70 until the head 69 engages the necked-down section 62 of the receiver 60. Movement of the head 69 within the receiver 60 exposes the openings 64 and 65 and allows the section 63 to fill with uid. After the head 69 engages the section 62 of the receiver, continued upward movement of the piston rod pulls the piston 57 upwardly, thus creating an area of reduced pressure within the lower portion of the chamber 46 and closing the check valve 52. The continued upward movement of the piston 57 functions to increase the area of reduced pressure within the lower portion of the chamber 46 until the lower piston or valve ring 59 passes the lower edge of the ports 47. At this instant, the area of reduced pressure within the chamber 46 is suddenly exposed to the liquid within the well. The potential energy of this liquid, in the form of hydrostatic pressure, is instantaneously converted to kinetic energy by the sudden influx of the liquid into the area of reduced pressure within the chamber. This influx results in a sudden implosion with resultant shock waves and subsequent tluid hammer, the magnitude and kinetic energy of which will depend upon the hydrostatic conditions within the well and the size of the void chamber. It is noted that the length of the housing member may range from 2 to 20 feet or more, and the depth of liquid in the well may be varied without departing from the invention.

At the instant the area of reduced pressure within the chamber is exposed to the ports 47, the spring 70 acts to accelerate the piston 57 upwardly with respect to the pisportion of the chamber and thereby maximizing the tools ton rod 61, thus, rapidly opening the ports 47 to the lower shock effect. Upward movement of the piston with respect to the piston is then decelerated by the hydraulic cushion created when the head 69 forces fluid through the restricted opening 65. At the point at which the lower portion of the chamber 46 is opened to the port 47, considerable tension is released from the piston rod, and the rod thus tends to accelerate upwardly within the chamber. Upward movement of the piston rod 61 is cushioned when the rod reaches the point wherein the cushion piston 73 secured thereto must force fluid through the relatively small passages 54 disposed at the upper end of the housing member.

At the end of the above-described sequence of operation, the shock-inducing tools of FIGURES 6 to 8 are in condition to be reactivated to produce subsequent shocks. Thus, the tool may be utilized to subject earth formations and harmful formation or casing scale-type precipitates to frequent and repeated shock forces. The embodiments of FIGURES 6 to 8 are particularly suited for frequent and repeated use, since they incorporate a minimum of components and, as a consequence, prove Very durable in operation.

The foregoing description of the invention is merely intended to be explanatory thereof. Various changes in the details of the illustrated constructions may be made, within the scope of the appended claims, without departing from the spirit of the invention. For example, in the embodiments of FIGURES 6 to 8, it is anticipated that deceleration of the piston with respect to the piston rod could be accomplished through means of a spring, rather than the hydraulic cushioning action within the receiver 68. Such a spring would have a compression position opposite to the tension position to absorb overtravel, thus eliminating the need of the hydraulic cushion within the receiver 60. Furthermore, in the embodiments of FIG- URES 6 to 6, although the cushioning means between the piston and piston rod and between the piston rod and housing are preferred, it is anticipated that these means may be omitted. Such an omission could be accomplished by using a rigid connection between the piston rod 61 and piston 57, and by eliminating the cushion piston 73 and the passages 53 and 54.

I claim as my invention:

1. A downhole shock-inducing tool adapted to be positioned in a body of liquid within a well at .a level opposite an earth formation to be treated which is in contact with said body of liquid, said tool comprising,

a longitudinal housing member of a diameter to pass down the well to the desired level, said housing member having a chamber formed therein and port means through a wall thereof to the chamber;

locating means secured to said housing member for positioning said housing member within the well above the bottom thereof;

chamber-evacuating means carried by said housing member for creating a condition of reduced pressure within a closed portion of the chamber; normally-closed valve means operatively associated with said chamber-evacuating means and said port selectively operating said chamber-evacuating means and said valve means. 3. A downhole shock-inducing tool adapted to be positioned in a body of liquid within a well at a level opposite an earth formation to be treated which is in contact with said body of liquid` said tool comprising,

a longitudinal housing member of a diameter to pass down the well to the desired level, said housing member having a chamber formed therein and port means through a wall thereof to the chamber;

locating means carried outwardly on said housing mem- `ber for positioning said housing member within the well above the bottom thereof;

a slide valve carried within said housing member for opening and closing said port means;

valve-restraining means carried by said housing member and operatively connected to said valve for keeping said valve in a normally closed position;

a piston slidably mounted within said housing mem- -ber for creating a condition of reduced pressure within a portion of the chamber, said piston being carried at the lower end of a piston rod;

a piston rod extending axially and vertically through one end of said housing member;

a check valve carried in said piston for permitting flow therethrough in one direction;

means carried by said piston rod for actuating said valve-restraining means to open said slide valve at substantially the end of a piston stroke creating said condition of reduced pressure, whereby said portion of the chamber wherein the condition of reduced pressure is created is suddenly exposed to the pressure of the liquid outside the housing member on the opening of the slide V-alve;

and, motion-transmitting linkage means operatively connected to the top of the piston rod and extending to the top of the well.

4. A downhole shock-inducing tool adapted to be positioned in a body of liquid Within a well at a level opposite an earth formation to be treated which is in contract with l@ said body of liquid, said well being lined with a well casing having at least one perforate section therein opposite the formation to be treated, said tool comprising, a longitudinal tubular housing member of a diameter means to close all of said port means with respect to to pass down the well 4to the desired llevel, said said portion of the chamber at least during the housing member dening achamber and having port evacuation thereof, said valve means being adapted means through a wall thereof to the chamber; to open said port means to said portion of the chamlocating means carried outwardly on said housing member after creation of said condition of reduced pres- =ber for engaging the well casing and positioning sure therein; 1o said` housing member within the well above the and, activating means connected to said chamber bottom thereof;

evacuating means for selectively operating said a slidable sleeve valve carried within said housing chamber-overwriting moans, member for opening and closing said port means; 2. A downhole shock-inducing tool adapted to be posilatch means carried by Said housing member for keep' tioned in a body of liquid within a well at a level opposite ing Said Valve in a normally closed position; an earth formation to be treated which is in contact with a piston slidably mounted within said housing memsaid body of liquid, said tooling comprising, ber for creating a condition of reduced pressure a longitudinal housing member of a diameter to pass Within a Por tion of the chamber, Said Piston "being down the well to the desired level, said housing mem- Carried at the lower end of a piston rod; ber having a chamber formed therein Iand port means 2O a Piston rod eXtending aXiauy and Vert-icaiiy through through a wall thereof to the chamber; one end of Said housing member; locating means secured to said housing member for a cheek Valve carried in said piston for permitting positioning said housing member within the well how therethrough in One direction; ,above the bottom thereof; means carried by said piston rod for actuating said a valve Carried by Said housing member for opening latch IIlSaIlS t0 Opell Said SleCVe ValV at ISlllJSlIZll'ltlZllly and Closing Said port means; the end of a plston stroke creating said condition valve-restraining means carried by said housing memof reduced Pressure, Whereby Said Portion of the ber and operatively connected to said valve for keep- .Chamber wherein `the condition of reduced Pressure ing Said valve in a normally closed position; 1s created by said pist-on stroke is suddenly exposed chamber-evacuating means carried by said housing 't0 the Pressure of the liquid outside the housing member for creating a condition of reduced pressure member on the opemng of the SieeVe VaiVe; Within a portion of the chamber; and, a cable secured to the top of the piston rodl and and, motion-transmitting linkage means operatively extendmg 'to the top of the Weil- `connected to said chamber-evacuating means and to 5- A'dOWhhole shoci'ldduclhg tool adapted to be Posisaid valve and extending to the top of the well for tlonedi 1n a body of hquld Within a Weil at a ieVe1 0P- posite an earth formation to be treated which is in contact with said body of liquid, said well being lined with a well casing having at least one perforate section therein opposite the formation to be treated, said tool comprising,

a longitudinal tubular housing member of a diameter to pass down the well to the desired level said housing member dening a chamber and having port means through a wall thereof to lche chamber;

locating means carried outwardly on said housing member for engaging the well casing and positioning said housing member within the well above the bottom thereof;

a slidable sleeve valve carried within said housing member for opening and closing said port means;

spring means carried by said housing member for keeping said valve in a normally closed position;

a piston slidably mounted within said sleeve valve for creating a condition of reduced pressure withinl a portion of the chamber enclosed by said sleeve valve, said piston being carried at the lower end of a piston rod;

a piston rod extending axially and vertically through one end of said housing member;

a check valve carried in said piston for permitting flow therethrough in one direction;

means carried by said piston rod for actuating said spring means to open said sleeve valve at substantially the end of a piston stroke creating said condition of reduced pressure, whereby said portion of the chamber wherein lthe condition of reduced pressure is created 'by `said piston stroke is suddenly exposed to the pressure of the liquid outside the housing member on the opening of the sleeve valve;

and, a cable secured to the top of the piston rod and extending to the top of the well.

6. A downhole shock-inducing 'tool adapted to be positioned in a body of liquid within a well at a level opposite an earth formation to be treated 4which is in contact with said ybody of liquid, said well being lined with a well casing having at least one perforate section therein opposite the formation to be treated, said tool comprising, `a longitudinal tubular housing member of a `diameter l-atch means carried by said housing member for keeping said valve in a normally closed position;

spring means carried within said housing member and in contact with said sleeve valve to close said valve;

a piston slidably mounted within said sleeve valve for creating a condition of reduced pressure within `a portion of the chamber enclosed by said sleeve Valve, said piston being carried at the lower end of a piston rod;

a piston rod extending axially and vertically through one end of said housing member;

a check valve carried in said piston for permitting ow therethrough in one direction;

means carried by said piston rod for actua-ting said latch means to open said sleeve valve at substantially the end of a piston stroke creating said condition of reduced pressure, whereby said portion of the chamber wherein the condition of reduced pressure is created by said piston stroke is suddenly exposed to the pressure of the liquid outside the housing member on the opening of the sleeve valve;

and, a cable secured to the top of the piston rod and extending to the top of the well.

7. A downhole shock-inducing tool adapted to be positioned in a body of liquid within a well at a level opposite an earth formation to be treated which is in contact with said body of liquid, said tool comprising,

a longitudinal housing member of a diameter to pass down the well to the desired level, said housing member having a chamber formed therein and port means through a wall thereof to the chamber;

locating means carried outwardly of said housing member for limiting the downward movement of said housing member within the well;

chamber-evacuating means carried by said housing member for creating a condition of reduced pressure within a portion of the chamber;

valve means carried by said chamber-evacuat-ing means 8. A downhole shock-inducing tool adapted to be positioned in a body of liquid within a well at a level opposite an earth formation to be treated which is in contact with said liquid, said tool comprising,

a longitudinal housing member of a diameter to pass down the well to the desired level, said housing member having a chamber formed therein and port means through a wall thereof to the chamber;

locating means carried outwardly of said housing member for limiting the downward movement of said housing member within the well;

a piston slidably mounted within said housing member for creating a condition of reduced pressure within a portion of the chamber, said piston being carried at the lower end of a piston rod;

valve means carried by said piston and slidably engaging the wall of said housing to close said port 'means with respect to said portion of the chamber, said valve means being adapted to open said port means to said portion of the chamber after creation of said conditi-on of reduced pressure therein;

a check valve communicating with said portion of the chamber to permit flow therefrom;

and, activating means operatively connected to the top of the piston rod to impart reciprocating movement thereto.

9. A downhole shock-inducing tool adapted to be positioned in a body of liquid within a well at a level opposite an earth formation to be treated which is in contact with said liquid, said tool comprising,

a longitudinal housing member of a diameter to pass down the well to the desired level, said housing member having a chamber formed therein and port means through a Wall thereof to the chamber;

locating means carried outwardly of said housing member for limiting the downward movement of said housing member within the well;

a piston slidably mounted within said housing member for reciprocating movement into and out of a portion of the chamber, said piston being adapted to create a condition of reduced pressure within said portion of the chamber upon movement out of said port-ion of the chamber;

Valve means carried by said piston and slidably engaging the wall of said housing to close said port means with respect to said portion of the chamber, said valve means being adapted to open said port means to said portion of the chamber after movement of said piston out of said portion of the chamber, whereby said portion of the chamber wherein the condition of reduced pressure is created is suddenly exposed to the pressure of the liquid outside the housing member;

a piston rod having a lower end secured to said piston for limited sliding translation with respect thereto;

resilient means coacting between said piston and piston rod to bias said piston towards said piston rod, said resilient means acting to bias said valve means to facilitate sudden opening of said port means upon movement of said piston out of said portion of the chamber;

a check valve communicating with said portion of the chamber to permit flow therefrom;

and, activating means operatively connected to the top of the piston rod to impart reciprocating movement thereto.

10. A shock-inducing tool according to claim 9 including shock absorbing means disposed between said piston and piston rod to cushion relative movement therebetween.

11. A downhole shock-inducing tool adapted to be positioned within a well at a level opposite an earth formation to be treated which is in contact with said body of liquid, said well being lined with a well casing having at least one perforate section therein opposite the formation to be treated, said tool comprising,

a longitudinal housing member of a diameter to pass down the well to the desired level, said housing member having a chamber formed therein and port means through a wall thereof to the chamber;

locating means carried outwardly of said housing member for engaging the well casing and limiting axial movement of said housing member within the well;

a piston slidably mounted within said housing member for creating a condition of reduced pressure within la portion of the chamber, said piston being carried at the lower end of a piston rod;

valve means carried by said piston and slidably engaging the wall of said housing to close said port means with respect to said portion of the chamber, said valve means being adapted to open said port means to said portion of the chamber after creation of said condition of reduced pressure therein;

and, motion-transmitting linkage means operatively connected to the top of the piston rod and extending to the top of the well.

12. A downhole shock-inducing tool adapted to be member having a chamber formed therein and port means through a Wall thereof to the chamber; locating means carried outwardly of said housing member and extending to the top of the well for suspending positioned `in a body of liquid Within a Well at a level opposite an earth formation to be treated which is in contact with said liquid, said tool comprising,

said Ihousing member at the desired level within the well;

a piston slidably mounted within said housing member a longitudinal housing member of a diameter to pass down the well to the desired level, said housing member having a chamber formed therein and port means for creating a condition of reduced pressure Within a portion of said chamber, said piston being carried at the lower end of a piston rod;

, through a wall thereof to the chamber; L) valve means carried by said piston and slidably engaglocating means carried outwardly of said housing meming the wall of said housing to close said port means ber and extending to the top of the Well for suspend- With respect to said portion of the chamber, said ing said housing member at the desired level within valve means being adapted to open said port means the well; to said portion of the chamber `after creation of said a piston slidably mounted Within said housing member for creating a condition of reduced pressure Within `a portion of said chamber, said piston being carried at the lower end of a piston rod;

valve means carried by said piston and slidably engaging the wall of said housing to close said port means with respect to said portion of the chamber, said Valve means being adapted to open said port means to said portion of the chamber after creation of said condition of reduced pressure therein;

a check valve communicating with said portion of the chamber to permit ilow therefrom;

a hydraulic activating motor secured to said housing member and operatively connected to the top of said condition of reduced pressure therein;

a check valve communicating wit-h said portion of the chamber to permit ow therefrom;

an electric activating motor secured to said housing member and operatively connected to the top of said piston rod to impart reciprocating movement thereto;

and, electrical leads extending between said electric activating motor and the top of the Well to supply electrical energy to said motor.

References Cited by the Examiner UNITED STATES PATENTS piston rod to impart reciprocating movement thereto; 1,086,050 2/ 14 Hoch et al 166-177 and, conduit means extending between said hydraulic 1,305,914 6/ 19 Mack 166-158 activating motor and the top of the well to convey 1,865,912 7/32 Horn 166-177 hydraulic fluid to said motor. 13. A downhole shock-inducing tool adapted to be CHARLES E. OCONNELL, Primary Examiner. 

1. A DOWNHOLE SHOCK-INDUCING TOOL ADAPTED TO BE POSITIONED IN A BODY OF LIQUID WITHIN A WELL AT A LEVEL OPPOSITE AN EARTH FORMATION TO BE TREATED WHICH IS IN CONTACT WITH SAID BODY OF LIQUID, SAID TOOL COMPRISING, A LONGITUDINAL HOUSING MEMBER OF A DIAMETER TO PASS DOWN THE WELL TO THE DESIRED LEVEL, SAID HOUSING MEMBER HAVING A CHAMBER FORMED THEREIN AND PORT MEANS THROUGH A WALL THEREOF TO THE CHAMBER; LOCATING MEANS SECURED TO SAID HOUSING MEMBER FOR POSITIONING SAID HOUSING MEMBER WITHIN THE WELL ABOVE THE BOTTOM THEREOF; CHAMBER-EVACUATING MEANS CARRIED BY SAID HOUSING MEMBER FOR CREATING A CONDITION OF REDUCED PRESSURE WITHIN A CLOSED PORTION OF THE CHAMBER; NORMALLY-CLOSED VALVE MEANS OPERATIVELY ASSOCIATED WITH SAID CHAMBER-EVACUATING MEANS AND SAID PORT MEANS TO CLOSE ALL OF SAID PORT MEANS WITH RESPECT TO SAID PORTION OF THE CHAMBER AT LEAST DURING THE EVACUATION THEREOF, SAID VALVE MEANS BEING ADAPTED TO OPEN SAID PORT MEANS TO SAID PORTION OF THE CHAMBER AFTER CREATION OF SAID CONDITION OF REDUCED PRESSURE THEREIN; AND, ACTIVATING MEANS CONNECTED TO SAID CHAMBER EVACUATING MEANS FOR SELECTIVELY OPERATING SAID CHAMBER-EVACUATING MEANS. 